1. Field of the Invention
The present invention concerns non-pathogenic lactic acid bacteria and food products containing the bacteria. The cell walls of these lactic acid bacteria are susceptible to the action of muramidase-type enzymes. The enzymes produce cell wall fragments called muramylpeptides that, when ingested, improve the quality of sleep.
2. State of the Art
Today many people have difficulty falling asleep or suffer from sleep disturbances such as insomnia. To reduce these problems, many pharmaceutical products containing benzodiazepines or barbiturates have been developed. However, these products should be administered under the care of a physician due to their secondary effects such as drug dependence, daytime sleepiness, memory loss, and interactions with other substances, notably alcohol.
Research on infectious diseases has shown that infection by pathogenic bacteria provokes at least three physiological responses in the infected subject: an immune response, fever, and modification of sleep. The mediators of these reactions in the host are components of the cell walls of the bacteria responsible for the infection, specifically muramylpeptides (and also lipopolysaccharides in gram-negative bacteria). Research has shown that the cell walls of pathogenic bacteria such as Staphylococcus aureus are hydrolyzed by macrophages to yield free muramylpeptides. (Johannsen L. et al., 1994).
To avoid the secondary effects of medicines containing benzodiazepines or barbiturates, U.S. Pat. No. 4,698,330 proposes to use compositions based on purified muramylpeptides that have somnogenic activity. Although the administration of these muramylpeptides leads to an increase of the deep sleep called Non Rapid Eye Movement (NREM) sleep, it also provokes an increase of body temperature, requiring the concomitant administration of antipyretic compounds.
Patent applications CH 654 330 A, CN 1 114 217 A and WO 8800438 A describe compositions containing bacteria, notably lactic acid bacteria, that improve sleep. However these documents do not reveal how lactic bacteria intervene in the improvement of sleep. The effect on sleep, as well as the other advantages claimed (more energy, better appetite and digestion, alleviation of rheumatism, etc.) of such compositions containing lactic acid bacteria are said to result from the specific balance of nutrients and micro-nutrients contained in the described compositions.